We propose to study resistance to and patterns of drug abuse among youth. A primary product of this research will be a series of cross-validated prediction scales and sequential decision strategies shown empirically to be optimal for various cohorts of youth, homogeneous according to several personal variables and patterns of drug abuse and resistance to drug abuse. We will first review the pertinent literature from the last fifteen years to discover predictor variables and items shown or believed to be related to patterns of youthful drug abuse. Then we will hold a working conference with a small number of experts in this area to seek additional recommendations about possible predictors, delineate problems associated with a socially sensitive study such as this, and develop solutions to these problems. We will also conduct informal workshops with small samples of youth to obtain their suggestions for approaches in conducting this study. With knowledge gained from the above sources, we will develop a comprehensive research questionnaire, administer it to large samples of youth, and, utilizing sophisticated statistical prediction methods combining multiple, stepwise, discriminant function analyses with moderator variable and configural pattern analyses, we will develop and cross-validate prediction scales and sequential decision strategies to predict resistance to drug abuse and type and extent of drug abuse.